Day 4 Tuesday July 19, 2011

We drove to the Great Sand Dunes today. My dad, Elizabeth, Matthew and I took a 2 mile hike up the overlook trail to see the dunes from the mountains that surround them.

The Sand Dunes are the tallest north America, rising about 750 feetrom the floor of the San Luis Valley on the western base of the Sangre de Cristo Range, covering about 19,000 acres.

The dunes were formed from sand and soil deposits of the Rio Grande flowing through the San Luis Valley. Over the ages, westerly winds picked up sand particles from the river's flood plain. As the wind lost power before crossing the Sangre de Cristo Range, the sand was deposited on the east edge of the valley. This process continues, and the dunes are slowly growing. The wind changes the shape of the dunes daily.